. >> reporter: for an entry into the united states, how difficult is it to get an admission ticket to america? citizens in 35 countries don't even need a visa to gain entry. as part of the visa waiver program, it allows them a maximum 90-day stay. but for those from other countries, travelers must apply for specific visas. there are temporary visas for tourists, business travelers, short-term employment, and students. each visa type allows a person to stay in america for different lengths of time. longer-term visa applicants need to show strong ties to their country of origin as proof they'll return home. student visas allow a person to stay for the duration of their studies. and more than 650,000 foreign students attended u.s. colleges and universities last year. temporary worker visas permit a three-year stay with roughly 100,000 issued per year. the most common tourist or business visas allow a six-month stay. immigrant visas are for those looking to become a permanent u.s. resident. those applicants need sponsors like an american relative or u.s. employer. the u.s. state departmen